1. Field of The Invention
The present invention relates to amine-complexed zinc salts of organic diacids, more particularly to amine-complexed zinc salts of dicarboxylic acids, diphenols, and phthalic acids, and to film-forming compositions containing such salts as corrosion inhibitors, for protection of metallic substrates susceptible to corrosion.
2. Description of The Prior Art
In the practice of corrosion control, as applied to ferrous and other metallic substrates susceptible to corrosion, e.g., iron, steel, copper, magnesium, aluminum and alloys thereof, a great number of metallic substrate treatment processes, such as passivation and phosphatizing, and anticorrosion coatings for such metallic substrates, have been developed and employed.
In particular, a large number of protective coatings for metallic substrates susceptible to corrosion have been disclosed and utilized in the prior art. Among such coatings formulations are various inorganic zinc silicate-containing compositions, in which zinc is employed as a pigment and filler in the inorganic silicate binder matrix. Such compositions have utility for coating of ferrous substrates, on which the zinc in the protective coating is galvanically sacrificed to reduce or inhibit corrosion of the underlying metallic substrate. Similarly, zinc chromate (in general commercial use as "Zinc Yellow" pigment) is widely employed in commercial paint and coating formulations, e.g., alkyd and latex paint formulations, but unfortunately it is characterized by a relatively high toxicity, which has limited its use in practice. A large number of organic protective coatings, and corrosion inhibitor pigments/additives for such coating compositions, have been developed.
U.S. Pat. No. 4,246,030 discloses a corrosion inhibitor for metals exposed to water, comprising a water soluble carboxylic acid and/or the salt thereof containing at least one hydroxyl group per molecule, and an amino alkylene phosphonic acid or derivative thereof, together with dispersing agents and other inhibitors such as molybdates, azoles and various inorganic metal compounds, including zinc oxide. The disclosed compounds include alkali metal salts of N-hydroxy ethylenediamine triacetic acid.
U.S. Pat. No. 4,217,142 discloses the use of magnesium azelate as a rust inhibitor for metal paints, preferably in combination with a basic oxide such as magnesium oxide. The patent specifically discloses that lead, calcium and zinc azelates in inert vehicles are unsatisfactory as corrosion inhibitors.
U.S. Pat. No. 2,816,051 discloses corrosion inhibitors which may be incorporated in primer coatings or volatile solvents for application to corrodible metals. The disclosed corrosion inhibitors are organic esters of certain acidic oxides of metals, including chromic acid, orthovanadic acid, metavanadic acid and molybdic acid.
A corrosion-inhibiting material for use in a coating composition is disclosed in U.S. Pat. No. 4,212,674, which comprises a fine particulate material such as natural crystalline calcium carbonate on which is coated a film of fatty amine or a fatty amine salt; the patent discloses that other conventional fillers, including kaolin, may be employed.
A surface treated filler material is disclosed in U.S. Pat. No. 4,191,670, as having utility in the preparation of emulsion paints, to improve the scrub resistance of such paints. The fillers, include natural and precipitated carbonates and silica compounds such as silicate including kaolin, mica and calcium. Such fillers are treated with a mixture of saturated and unsaturated aliphatic carboxylic acids. Such treated mineral fillers are disclosed to be particularly suited for water-based coating systems including acrylates and acrylic acid co-polymer systems.
U.S. Pat. No. 4,427,448 discloses a removable, oil-based corrosion inhibitor containing an aliphatic primary amine, an organic fatty acid plus an organotin compound and a glycolester.
Corrosion inhibitor for water-based latex paints designed to combat both pre-and post-drying rusting is disclosed in U.S. Pat. No. 4,243,417. The corrosion inhibitor has a formula M(Z).sub.x An, where M is a metal cation, An is a corrosion-inhibiting anion, and Z is a complexing volatile component, such as amino or alkylamino.
U.S. Pat. No. 3,306,908 discloses reaction products of high molecular weight hydrocarbon succinic acid compounds, amines and heavy metal compounds such as zinc or zinc oxide, which are useful as paint additives and impart corrosion-inhibiting characteristics. U.S. Pat. No. 3,163,603 discloses amide and imide derivatives of metal salts of substituted succinic acids and their use as corrosion inhibitors.
Rust-preventative paint compositions are disclosed in U.S. Pat. No. 3,876,574, which comprise polycarboxylic acids and compounds of metals such as zinc.
U.S. Pat. No. 2,689,828 discloses a mineral oil composition containing a corrosion inhibiting agent prepared from a phthalic acid, an alkyl-substituted phthalic acid or its anhydride, and a primary, secondary or tertiary amine.
Although as shown by the foregoing, numerous anticorrosion coating compositions and corrosion inhibitor additives have been developed in the prior art, there is nonetheless a continuing need for the development of improved corrosion-inhibiting additives and coating compositions containing the same, which are non-toxic or of reduced toxicity relative to the zinc chromate additive and compositions which are in commercial use.